Evaluation of the immune benefits of two probiotic strains Bifidobacterium animalis ssp. lactis, BB-12 ® and Lactobacillus paracasei ssp. paracasei, L. casei 431 ® in an influenza vaccination model: A randomised, double-blind, placebo-controlled study

The present study investigated the ability of Bifidobacterium animalis ssp. lactis (BB-12 ^®) and Lactobacillus paracasei ssp. paracasei (L. casei 431 ^®) to modulate the immune system using a vaccination model in healthy subjects. A randomised, double-blind, placebo-controlled, parallel-group study was conducted in 211 subjects (56% females, mean age 33•2 (sd 13•1) years). Subjects consumed a minimum of 10 ⁹ colony-forming units of BB-12 ^® (capsule) or L. casei 431 ^® (dairy drink) or a matching placebo once daily for 6 weeks. After 2 weeks, a seasonal influenza vaccination was given. Plasma and saliva samples were collected at baseline and after 6 weeks for the analysis of antibodies, cytokines and innate immune parameters. Changes from baseline in vaccine-specific plasma IgG, IgG1 and IgG3 were significantly greater in both probiotic groups v. the corresponding placebo group (L. casei 431 ^®, P = 0•01 for IgG; P <0•001 for remaining comparisons). The number of subjects obtaining a substantial increase in specific IgG (defined as ≥ 2-fold above baseline) was significantly greater in both probiotic groups v. placebo (BB-12 ^®, P <0•001 for IgG, IgG1 and IgG3; L. casei 431 ^®, P <0•001 for IgG1 and IgG3). Significantly greater mean fold increases for vaccine-specific secretory IgA in saliva were observed in both probiotic groups v. placebo (BB-12 ^®, P = 0•017; L. casei 431 ^®, P = 0•035). Similar results were observed for total antibody concentrations. No differences were found for plasma cytokines or innate immune parameters. Data herein show that supplementation with BB-12 ^® or L. casei 431 ^® may be an effective means to improve immune function by augmenting systemic and mucosal immune responses to challenge.